docs: def highshelf(self, gain=-20.0, frequency=3000, slope=0.5):
          """highshelf takes 3 parameters: a signed number for gain or
          attenuation in dB, filter frequency in Hz and slope (default=0.5).
  
          Beware of clipping when using positive gain.
          """
          self.command.append('treble')
          self.command.append(gain)
          self.command.append(frequency)
          self.command.append(slope)
          return self